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Chordata
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Four major characters: Notochord, Dorsal hollow nerve cord, Post-anal tail, Pharynx with gill slits
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 3 subphylum: Urochordata, Cephalochordata, Vertebrata
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Class Enteropneusta: Deposit/suspension feeders, Asexual & sexual reproduction, Some Tornaria larval stage
2
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Urochordates
Three classes
1
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Larvaceans: solitary, luminescent, planktonic, retain larval features, paedomorphosis Megalodicopia hians 3
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• Special features: Crainata, Duplication Hox gene complex, Neural crest – embryonic tissue, lots new structures
• Mineralised tissue late Cambrian → Bone fragments → Ostracoderms in early Ordovician ~480mya → Complete fossils late
Ordovician Bolivia, Australia e
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Astraspis
• Conodonts: Microfossils Cambrian-Triassic made of Apatite
Origin of bone and other mineralised tissue
• Tissues CaCO 3 & Ca 5(PO 4 )3, Link to Ostracoderm armour
• Teeth evolved several times
Eight groups
Myxinoidea (hagfish), Chondrichthes / Elasmobranchii (cartilaginous fish), Osteichthyes (bony fish), Amphibia (frogs,
salamanders), Reptilia (crocodiles, dinosaurs, snakes), Aves (birds), Mammalia (mammals), Petromyzontia (lampreys)

Agnatha (Jawless fish)
General characteristics:
• Slender eel-like bodies
• Naked skin, No scales
• Cartilaginous skeleton/ cranium
• Notochord persistent
• No vertebrae, No jaws
• 5-16 pairs Gills
• Distinct brain
• No distinct stomach

Class: Myxinoidea Hagfish
• All marine
• Skull cartilage, no jaws or vertebrae
• Attach toothed keratinised plats
• 3 accessory hearts + main heart
• both ♀ & ♂ gonads (1 functional)
• Skewed sex ratios poss 100♀ :1 ♂

Class: Petromyzontia (Lampreys)
• Marine & Freshwater
• Arcualia, cartilage pipe around notochord
• ~50% Parasitic, up to 1m long
• Velum – no H2O to mouth
• Anadromous - ascend rivers to breed
• Larval stage lasts 3-7+yrs
• Ammocoetes
• Great Lakes collapse 1950’s

Gnathostomata (jawed fish)

Ostracoderms

Silurian – mid Ordovician with improved locomotion, sensory & circulatory
systems, 2nd Hox duplication event
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Ventral mouth, overhanging rostrum
2
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Thicker, complex enamel teeth

Mesozoic Radiation
• Locomotor & feeding systems
• Hybodonts – Mouth terminal
• Heterodont dentition
• Living Hornsharks, similar
• Ceratotrichia: Long, flexible, fibrous
rods that support the fins of sharks
and other fish whose skeletons are
made of cartilage
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Sarcopterygii: extend central shaft bone, feather
2
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0010
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g
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Hempisphere only, FW & Marine
• All breed in FW

Neopterygians

Chondrosteans (paraphyletic group):

Acipenseriformes: Paddlefish
• ~30 extant species, most Red listed
• 2 extant species
• ↓↓ dermal ossification
• Large rostrum, Ampullary Organs

Piscivorous Amiiformes: Bowfin
(1sp)
• Single layer scales
• Jaw modified suction
• Asymmetric caudal fin
• Eat anything

Polypteriformes: Birchirs, Reedfish
• 11 extant species
• Flag-like dorsal finlets
• Well ossified skeleton
• Ganoid scales – ganoine
• Ventrally placed lungs

Lepisosteiformes: Gars (7 sp)
• 1-4m, FW & Estuaries
• Warm temperate regions
• Interlocking multilayered scales

Class: Actinopterygii (Ray-finned fishes)
Teleosteans: every other fish!!!
• 27,000 species
• 4 clades
1
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Elopomorpha: ~800 sp Late Jurassic, marine Leptocephalus larva
3
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Euteleostei: the rest!! mid-late Cretaceous Lots groups Ostariophysi: Weberian
Apparat + Alarm substance skin
Why so many teleosts?
• Cycloid & ctenoid scales
• mobility & speed
• Homocercal tail
• Elaboration fins
•  efficiency gas resorption & secretion
• Changes jaw suspension

Holocephalians: Ratfishes,
Chimeras & Ghost sharks
• ~35 species
• Shark like & bony fish
• Diverged shark lineage 360mya
• Ground dwelling, deep water
• Mixed diet, fused tooth plates
• Autostylic jaw
•Cephalic claspers, oviparous
• Poisonous spines

Origin & Radiation of the Tetrapods
• Air Density, Gravity, Bone, Oxygen content
• Haversian systems
• Joints encased in synovial fluid
• Gnathostome that has limbs
• Early Devonian (~400mya)
• 4 major adjustments

• Closely related to Osteolepiforms, Eusthenopteron and Panderichtyes
• Eusthenopteron: bones that resemble humerus, radius & ulna, wrist bones
• Tiktaalik: well developed gills, no operculum, modified pectoral fins
• Acanthostega: well formed limbs, digits, gill bones, pectoral & pelvic girdles
weak, couldn’t walk on land, tail fin rays
• Ichthyostega: well developed limbs & muscle, could walk on land, not very well,
tail fin rays

Amniotes (Tetrapods that have a
terrestrially adapted egg)
1
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Sauropsida →Mesosaurs, 2o aquatic
3
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Eureptiles →Diapsids →lizards, snakes, plesiosaurs,
ichthyosaurs, dinosaurs, crocodilians & birds

Amphibians
• Amphibians are tetrapods that do NOT have amniotic eggs
• Come from group Lissamphibians, branch of Temnospondyli
• Diversified during Carboniferous
• ~5400+ species
• Three chambered heart
• Double circulation system
• Spend part of their time on land
• Respiration via lungs, skin, gills
• Metamorphosis usually present
• Return to water / v
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Order: Apoda (Gymnophiona): Caecilians ~170 species
2
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Order: Anura (Salientia): frogs & toads ~5,420 species

Shared derived characteristics
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Papilla amphibiorum: sensory area ear <1000Hz
3
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Green rods: distinct retinal cells
5
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Levator bulbi muscle structure: orbit cavity, eye bulging → ↑buccal
cavity
Amphibian respiration
• Positive pressure breathing to inflate lungs
• 1st step: Muscles lower floor oral cavity→ air in via nostrils
• 2nd step: close nostrils and mouth, floor oral cavity rises, air forced
down trachea
• Exhale using elastic recoil of the lungs & compression of muscular
body wall

Order Apoda (Gymnophiona):
Caecilians
• "Naked Snake" or "legless ones"
• Eocaecilia, Early Jurassic
• Annuli – dermal folds, scales
• Eyes ↓, skin, bone covered, blind
• Protrusible tentacles
• Haderian gland
• Some spp lay eggs, parental care
• Viviparity (75%), Matrotrophy

Order Urodela: salamanders & newts
• Also known as Caudata
• 8 families
• Carnivorous all life stages
• Lack ribs – breathing
• Territoriality (some)
Reproduction:
• Hedonic & Mental glands
• ♂ pass spermatophore
• Viviparity
• Amphiumas loses gills before
adulthood

• Some salamander spp entirely terrestrial but lack
lungs e
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Plethodontidae
• Rely on cutaneous respiration
• Buccopharyngeal breathing: gas exchange over
mouth membranes
• Some spp have gills their whole life e
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axolotl
• Exhibit paedomorphosis
• Non-metamorphic spp like Necturus & Axolotl
• Metamorphic spp change when environmental
conditions are poor e
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Ambystoma tigrinum

Order Anura (Salientia): frogs & toads
• Lots families see e
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Ranidae, Hylidae, Bufonidae
• Head and trunk fused
• Good vision
• Specialised for jumping , walking
• External & internal gills
• Specialised mouthparts
• Adult carnivorous
• Aposematic Colouration
• Undergo hibernation
• Some spp have anti-freeze via glycogen and glucose
+ urea into tissues
• Survive freezing of up to 65-70% of their body water
• Take uninterrupted freezing for ≥ 4 weeks

Hylidae & Rhacophoridae: Arboreal (tree) frogs
• Large toe pads
• Skin layer, peglike projections
• Mucus glands → viscous fluid
Gastric Brooding Frogs Rheobatrachus sp
• Female swallows fertilised eggs
• Jelly contains Prostaglandin E2
• Young nourished by large egg yolk
Current threats to amphibians
• Habitat loss, climate change
• Chytrid fungus & rana viruses
• Chytridiomycosis: affects skin, respiration
• 9 species definitely extinct, possibly another 113

Turtle
Evolutionary History
• Oldest reptile fossils 310mya, late Carbonfierous
• Parareptiles: e
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Slow rate molecular evolution
• Dorsal shell (carapace) ventral plastron
2
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Identical chromosome number & structure
• Keratinised horny beak
• Juvenile pelagic stage

Lepidosaurs
Origins & radiation
• Oldest fossil 310mya, Parareptiles
Placodonts e
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Walrus turtles
• Triassic period
• Stocky, short legged, Large flat teeth
• Front teeth projected forward
Pleisosaurs
• Late Triassic è Cretaceous
• Heavy bodied
• Oar like limbs:
• Plesiosauriods and Pliosauriods

Modern reptiles:
Order: Sphenodontia, Tuataras
• Diverse Mesozoic
• Primitive Diapsid skull
• Acrodont tooth arrangement
• 2 living species
• 3 chambered heart
• Don’t replace teeth
• Eyes focus independently
• No eardrum , earhole, mid ear fatty tissues
• Operate low temperatures
• Hibernate, winter
• Slow growing, 20yrs mature
• 2-5yr reproductive cycle

Ichthyosaurs
• Triassic è Cretaceous
• Jurassic highest diversity
• Dolphin/Shark/fish like
• Viviparous
• Cephlapods i
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ammonites
Mosasaurs
• Late Cretaceous
• Crocodile with flippers
• 3-17m in length
• Elongate skull
• Viviparous



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